Rolling of aluminous metal foil



United States Patent 3,105,400 ROLLD G OF ALUMINOUS METAL FOE Vern L. Goppelt, New Kensington, la., assignor to Aluminum Company of America, Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Filed May 10, 1954, Ser. No. 428,833 4 Claims. (Cl. 8060) This invention relates to the cold rolling of the light gauge metal sheet product known as foil and imparting to the sheet a coating which is advantageous in subsequent forming operations. The invention has particular application in cold rolling aluminous metal foil and use of the resulting product. The tenm aluminous metal as used here refers .to both aluminum of any grade and those alloys wherein aluminum constitutes not less than 80% of the total composition. The term foil refers to a class of thin sheet products usually less than 0.006 inch in thickness.

It has been a common practice in cold rolling aluminous metal foil to use as a roll lubricant mineral oil with or without the addition of animal or vegetable fats or oils to minimize a sticking of the metal to the rolls and to lubricate the interface between the rolls and the metal. Although the use of such lubricants has overcome difliculties associated with rolling without any lubricant, yet it has many shortcomings, chief among them being the inability of any residual film to protect the foil against scratching and tearing in subsequent forming operations. In other cases the oil film is objectionable on the final product and hence must be removed either before or after the article is formed. It may also interfere with the application of certain finishes.

For the purpose of improving the ease of forming the foil articles it has been proposed that the finished foil should be given a coating of stearic acid by passing it through a solution of the acid in a volatile solvent. Subsequent to the immersion the foil must be dried in order to remove the solvent. Such a coating operation is of course expensive and is not suitable where a low cost item is to be fabricated from the foil. Moreover, the stearic acid coating is dull and possesses a greasy feeling which is undesirable in many cases. Lastly, the stearic acid does not have as high a lubricating value as demanded in many severe forming operations.

It is an object of this invention to provide an improved foil product, especially in :al-uminous metal product, which can be easily formed. Another object is to provide improved lubrication in the cold rolling of metal foil, particularly aluminous metal foil. A further object is to provide a low cost method of applying the improved lubricant to foil. These and other objects and advantages will become apparent from the following description and examples of the invention.

1 have found that butyl stearate alone or in a composition principally composed of that stearate is an excellent lubricant in cold rolling metal foil, particularly aluminous metal foil, and that it forms a bright nonagreasy film on the foil which protects the foil from abrasion by forming tools, minimizes tearing, and protects the highly polished tool surfaces from abrasion by the foil. Butyl stearate appears to possess unique properties as a lubricant in effecting a reduction in the foil during rolling and in subsequent forming operations. Since it is a liquid at room temperature and pressure it can be directly applied to the rolls and it becomes uniformly distributed over the foil surface during rolling with the result that the product is uniformly coated with butyl stearate.

The butyl stearate initially used should be of at least commercial purity, that is, it should contain at least 97% of the ester. Butyl stearate of such a purity is referred to herein as being pure. The impurities found in the com- 3,105,400- Patented Oct. 1, 1963 ice mercially pure product have not been found to have any adverse effect upon the behavior of the stearate or the quality of the foil product. Additives should not be introduced into the stearate which would have a deleterious effect on it, such as interfering with the flow characteristics, the load bearing qualities, or the forming ability of the foil product. The commercially pure butyl stearate generally consists of the normal stearate, however, those varieties having a branched butyl radical are also useful. in the course of employing butyl stearate on a mill having a roll lubricant circulation system some dilution of the stearate occurs over a period of time because some oil from the mill and even the incoming sheet stock are picked up. Such diluents can be tolerated, it has been found, providing the butyl stearate content of the roll lubricant does not go below 70%. Such a mixture is re garded as still being essentially butyl stearate since the desired properties of the compound are dominant. In some cases it may be desirable to intentionally dilute the butyl stearate and this can be safely done by adding volatile hydrocarbon liquids. The hydrocarbon quickly evaporates from the foil leaving a coating of the butyl stearate.

The butyl stearate is applied to the rolls in the same manner as previous rolling lubricants, that is, through perforated pipes extending across the face of the rolls or on the foil entering the rolls. In any case the butyl stearate is present at the interface between the rolls and the metal during rolling. Although the liquid butyl stearate can be applied in an amount just sufficient to provide the necessary lubrication in usual rolling practice, the rolls are flooded with the lubricant which is collected and re-circulated. In some cases it may be desirable to warm the butyl stearate to reduce its viscosity and thereby improve the ease of applying it to the rolls and foil, but such a procedure is not ordinarily necessary.

The new lubricant is employed in at least the last roll pass in order to provide the necessary film upon the [foil product. Increased benefits from the use of butyl stearate may be realized by using it in the roll passes immediately preceding the final pass. It has been found that greater reductions in thickness can be made per pass where this lubricant is used than where the conventional type of mineral oil is employed. It is therefore possible in many cases to use a smaller number of roll passes to obtain the desired foil thickness than has been possible heretofore.

The foil issuing from butyl stearate lubricated rolls is exceptionflly bright and does not have a greasy appearance or feeling, yet it can be successfully used in severe forming operations without any signs of being scratched or torn. Moreover, the film has no objectionable odor and is not harmful to food products, it is therefore not necessary to clean the foil either before or after an article is formed therefrom. Foil stock made in the foregoing manner has been successfully used in the production of such food containers as pie plates.

Not only can aluminum of ordinary purity and even high purity be satisfactorily rolled with butyl stearate lubricant but it has also been employed in the rolling of such alloys as aluminum-1.2% manganese, aluminum- 0.8% magnesium and aluminum-1.4% magnesium.

As indicated above, this invention is particularly applicable in the rolling of foil stock under the conditions normally used for fabricating such a product. Although the stock may initially be of a thickness as much as 0.025 to 0.030 inch yet the final product is a foil less than 0.006 inch in thickness, usually Within the range of 0.0025 to 0.0055 inch.

Examples wherein butyl stearate have been used are given below.

Cold rolled stock of commercially pure aluminum 0.022 inch in thickness was cold rolled in conventional manner to a thickness of 0.0075 inch using a mineral oil lubricant. The foil was then given .a final pass reducing the thickness to 0.0035 inch; thus effecting a reduction of 53% butyl stearate of commercial purity being applied to the rolls. The foil product had a bright appearance and was evenly coated with the butyl stearate. Pie plates were formed from' this foil without any scratching of foil or forming tools and no tearing of the foil.

In another case cold rolled stock of an aluminum 1.2% manganese alloy 0.015 inch in thickness was cold rolled to 0.0045 inch in a single pass by applying commercially pure butyl stearate to the rolls. The 70% reduction thus obtained was made possible by the use of the butyl stearate, whereas a minimum of two passes would have been required had the normal mineral oil lubricant been employed. The foil obtained through use of the butyl stearate had a very bright appearance and was uniformly coated with the stearate. Upon measurement vit was determined that the foil was covered with 1.5 mgs./ sq. foot of butyl stearate. This foil product was formed into pie plates without any scratching of either the foil or the forming tools and no tearing of the foil was encountered.

In another example 0.022 inch thick stock of an aluminum-1.4% magnesium alloy was cold rolled to 0.0045 inch thick foil in two passes using butyl stearate as the roll lubricant. The presence of the butyl stearate on the foil entering the final pass was considered to be of great value in effecting the large reduction on the second pass. Had a mineral oil lubricant been used, three passes would have been required. The foil produced with the butyl stearate roll lubricant had a bright surface and was uniformly coated with the stearate. Pie plates were satisfactorily formed from this foil without scratching of the foil or the forming tools and without tearing of the foil.

Having thus described my invention and certain embodiments thereof, I claim:

1. In a method of cold rolling metal foil the step comprising supplying to the interface between the rolls and the foil a composition consisting essentially of butyl stearate whereby a greater reduction can be obtained per roll pass than with a mineral oil lubricant under the same rolling conditions and the foil becomescoated with said butyl stearate.

2. In a method of cold rolling aluminous metal foil the step comprising supplying to the interface between the rolls and the foil a composition consisting essentially of butyl stearate whereby a greater reduction can be obtained per roll pass than with a mineral oil lubricant under the same rolling conditions and the foil becomes coated with said butyl stearate.

3. In a method of cold rolling metal foil the step of applying to the rolls during the rolling operation a composition consisting essentially of butyl stearate whereby a greater reduction can be obtained per roll pass than with a mineral oil lubricant under the same rolling conditions and the foil becomes coated with said butyl stearate.

4. In a method of cold rolling metal foil the step comprising supplying to the interface between the rolls and foil during the last pass of the rolling operation a composition consisting essentially of butyl stearate whereby a greater reduction can be obtained per roll pass than with a mineral oil lubricant under the same rolling conditions and the foil becomes coated with said butyl stearate.

References Cited in the file of this patent UNITED STATES PATENTS 281,784 Neilson July 24, 1883 1,225,044 Lauber May 8, 1917 1,996,392 Torrence Apr. 2, 1935 2,108,641 Blodgett Feb. 15, 1938 2,126,128 Montgomery Aug. 9, 1938 2,174,720 Edwards Oct. 3, 1939 2,179,067 Smith Nov. 7, 1939 2,236,590 Backofi Apr. 1, 1941 2.289,127 Koch July 7, 1942 2,411,024 Bruun Nov. 12, 1946 2,529,188 Rocchini Nov. 7, 1950 2,529,189 Rocchini Nov. 7, 1950 2,529,191 Rocchini Nov. 7, 1950 2,611,744 Kipp Sept. 23, 1952 2,613,626 Whitney Oct. 14, 1952 2,659,252 Kipp Nov. 17, 1953 OTHER REFERENCES Condensed Chemical Dictionary, 4th ed., Reinhold Publishing Co., O. 

1. IN A METHOD OF COLD ROLLING METAL FOIL THE STEP COMPRISING SUPPLYING TO THE INTERFACE BETWEEN THE ROLLS AND THE FOIL AN COMPOSITION CONSISTING ESSENTIALLY OF BUTYL STEARATE WHEREBY A GREATER REDUCTION CAN BE OBTAINED PER ROLL PASS THAN WITH A MINERAL OIL LUBRICANT UNDER THE SAME ROLLING CONDITIONS AND THE FOIL BECOMES COATED WITH SAID BUTYL STEARATE. 